CHICAGO  Turning his back to the rest of the locker room, Ryan Mathews dressed slowly and silently. Surely knowing what people wanted to talk to him about, and clearly not the least bit interested in sharing an explanation with anyone, Mathews twice was approached for comment after the game that turned on his latest fumble.

Muttering something unintelligible, he walked away. Asked again a few moments later to handle a few questions, he whispered something that must’ve amounted to “no comment,” and then he hit the exit in a flash.

“When you’re a running back and carrying the ball, that’s your baby, and you want to hold it tight,” said fellow running back Mike Tolbert. “When you don’t, when it gets away from you, it hurts.”

By no means was Mathews alone in feeling the pain of a fifth straight loss. There were plenty of teammates around him who decried their own play, trying to take the burden of blame on their shoulders, but Mathews’ second fumble of the game was even more crucial than the two interceptions thrown by Philip Rivers in the fourth quarter. Or any of the many other mistakes, for that matter.

With the Chargers trailing 24-17, more than five and a half minutes remaining in the third quarter and San Diego moving the ball well on the Bears, Mathews was given the ball on the first play of a drive and showed his strong burst for a 6-yard gain. The ball was punched out of his hands by cornerback Charles Tillman, who also recovered the fumble at the San Diego 37-yard line, and all the Bears needed were two snaps to make it a two-touchdown lead.

“It’s like Ollie (Wilson) always says,” said Tolbert, referring to the running backs coach. “It’s the guy you don’t see who knocks it out.”

As it happened, the ensuing touchdown was made possible by another misplay. The 24-yard pass went to wide receiver Johnny Knox, who had Cason still looking backwards as he watched the ball into his outstretched fingertips.

“I thought I was in great position,” said Cason. “You know, you turn around to locate the ball and it’s on the other side of you. I’ve got to find a way to make that play. I really, really thought I was in good position. To have something like that happen, it’s definitely unfortunate. Once again, I have to find a way to make that play, no matter what.”

Almost verbatim, those were the same kind of words Cason had uttered after the Chargers’ road loss to the New York Jets. Three of the New York touchdowns were scored on Cason’s coverage by Plaxico Burress, who until that seventh game of the season had been largely ineffective since joining the Jets out of prison. Likewise, the wonder in Chicago had been about the lack of offensive production by Knox, who’d caught a total of five passes in the previous three games and nine in the previous five.

Knox had three receptions for 97 yards Sunday, including a 42-yarder that led immediately to a 1-yard touchdown dive by quarterback Jay Cutler. The latter later was aiming again for Knox in the fourth quarter, but the receiver slipped to the ground and Cutler’s pass went right to Cason, who seemed to have a good shot at a long touchdown return.

“I wanted to score,” said Cason. “My mind-set was, get the score, and I thought I had it.”

Instead, running back Matt Forte took an angle and pushed Cason out of bounds at the Chicago 16-yard line. Whereupon one pass by Rivers went off Tolbert’s hands and another was intercepted in the end zone. Before it was over, Rivers had thrown another, making it seven games this season in which he’s been picked off at least twice.

“Yeah, I was throwing it away,” said Rivers of the second interception. “It’s almost embarrassing to say that I was throwing it away because when you throw it away, you want to make sure nobody gets it. I should have thrown it up there in the third row.”

Even when things went right for the Chargers, they went wrong. A challenge and replay negated a 10-yard touchdown pass to Earl Bennett, but because Cason was called for illegal use of the hands, the Bears got an automatic first-and-goal that soon was converted to a touchdown.

Conversely, a holding call on the Bears only temporarily took some of the sting out of a punt that Mike Scifres would’ve liked the back, relatively low drive in the second quarter that went right to Devin Hester. Hester already had returned one Scifres punt for 37 yards, but he went 42 yards to the Chargers 5, though the penalty had the Bears starting that next touchdown drive instead from the 41.

“He’s a great returner who made a great play on one, but one was just a bad punt,” said Scifres. “It wasn’t anything like what I wanted to do. Everything was in it, but I just made a bad kick. Fortunately, we got the holding call to knock them back a bit. But (Hester)’s so good, as a punter going against a returner and special teams like that, I can’t do something that puts my team in a position that’s hard to recover. And that’s what I did.”